Cellular carriers expend significant resources in terms of equipment and technical personnel to continue to meet the needs for high reliability and failover mechanisms in order to maintain signals for calls and associated services to subscribers. The rapidly changing cellular technology places demands on the carriers to not only maintain existing systems but to incorporate new or updated equipment in the field and other locations. Such changes can introduce equipment incompatibilities that can require reconfiguration of physical systems in terms of rack space as well as electrical incompatibilities that further require signal conditioning to meet existing interfaces.
Moreover, with the mix of cellular bands and technologies required in many locations to support coverage for sectors and cells, for example, tower stations now become a blend of equipment ranging from legacy hardware to updated hardware to proprietary systems in support of other services, and so on. In other words, co-siting further complicates systems and support of those systems by the difference in interconnections, signals levels, equipment form factors, etc. The expense involved with outright replacing old equipment with new equipment and the personnel training can be enormous.